For the past several years the neuroanatomical connections of the cerebral cortex of the rhesus monkey have been investigated using primarily the Nauta and Fink-Heimer silver impregnation techniques. These investigations have provided an increasing understanding of the cortico-cortical connections from the points of view of interhemispheric, intra hemispheric and cortico-limbic organization. In the present application two specific research directions are proposed which have emerged from and depend upon our current studies. One phase of the research plan will be devoted to seeking further information regarding the organization and connections of the cortical association and para-limbic areas. Specific emphasis will be placed on understanding the laminar organization of afferent input to these areas as well as the pattern of afferents to the other regions of the cerebral cortex. To pursue these problems additional techniques including autoradiography, electron microscopy and retrograde transport of horseradish peroxidase will be utilized in conjunction with the ablation and silver impregnation methods. A second phase of the research plan will address itself to behavioral questions directly related to the organization of cortico-cortical connections of association areas.